Valyrian steel is an alloy of steel and dragonglass melted together with dragon breath. The only reason it couldn't be produced was because dragons had been extinct for quite some time. Now that they're back, time to start up the forges! Those Others aren't going to stab themselves.

They've had a semi-official cover for WoW for almost a decade. There is absolutely no reason why they couldn't paint a cover for WoW, DoS, and the eight novel Springtime for Hodor right now and wait another 30 years for the writer to catch up.

Hypothermia wouldn't have been as big a deal. Grown men know how to spoon if facing death by ice. The lake freezing would have been worse, but as soon as it froze over enough to fool a bunch of stupid wights, they'd have just shambled across until another hole broke, so again, Jon & Co. might have survived a couple days there. If anything, having a massive battle on top of a freshly frozen lake, as the show did, would have been more unrealistic.

There's no other option in the North, however. In the west you have Westerlands and the Reach. In the south there's Dorne and Stormlands. In the East there's the Vale of Arryn and Stormlands. And the Riverlands' Lord could serve as a Warden in any direction. In the North, you only have the rulers of Winterfell or the Lord Commander of the Night's Watch, who can't serve as a Warden of the North and get involved in politics. How are you going to name a Warden of the North who isn't even in the North? If they pick, say, Jaime, he can't even get past the Neck, much less occupy the North and rule its subjects. The best they could hope for is to appoint a different Northerner, say Manderly, as Lord Paramount, and divest Winterfell of its ruling position. But then good luck getting the ruler of Winterfell in his strategically awesome position to go along with that.
It's going to be Ramsay, no matter what the Crown might otherwise desire. Besides, they don't exactly know what he's like and would probably just appoint him as a matter of routine paperwork drill.

All the factions of Westeros will have lost tons of fighters by the end. The final battle royale for the Iron Throne will consist of a dozen old women and children facing off against another dozen women and children with sticks and stones. Daenerys will have to ride a flightless emu into battle. And then the Others will invade.

He's not going to reverse it. That death in the show was awesome and one of the only parts of Season 6 that felt like 100% GRRM. If he did, then the show would upstage him. My previous entry on this subject was rather tongue-in-cheek. I'm sure it'll be easy enough to write Meera and Bran out of the heart tree and back south of the wall without Hodor's mighty dragging skills. Bran can warg direwolves, and direwolves can mush, for example.

Brienne and Jamie will fight to the death. Jamie will obviously die because of the whole missing hand thing. Brienne will get seriously upset with Lady Stoneheart and will not shut up about how unjust it was to kill Jamie until finally Lady Stoneheart gets tired of her bitching and resurrects Jamie, renaming him Ser Golden Pimp Hand and making him swear to kill off any Frey he meets, which he's only too happy to do.

Here's how to tie up loose ends in Winds of Winter:
Aegon meets a grisly end in Storm's End because Stannis and Melisandre forgot to tie up their ghostbabies, and ghostbabies get bored when they can't go 'a killin'. Most of the Golden Company sinks to the bottom of the ocean in those dang winter storms, while the rest get smashed by the Stormlanders.
Quentyn Martell isn't actually dead; the body belonged to someone else, which he in fact used to feed and tame a dragon. He then uses said dragon to fly over to Daenerys and fast travel her slow ass to Westeros. She's greeted with open arms in Dorne and together they lay waste to the southern half of Westeros. The rest of Essos is left scratching their butts, wondering what the fuck happened? Oh, yeah, Tyrion tames another dragon and flies his ass out of that plot-sucking shithole too.
Bran downloads the Cliff Note's version of the history of Westeros while his companions build a bunch of dogsleds. Bran then wargs into, like 40 direwolves at once and they mush on back to the Wall, trampling any wights or Others that get in their way. Hodor makes his way to Mole's Town, gets really excited at the door to the brothel, and it suddenly dawns on everyone that he's been talking about a Ho Door this whole time and just really needed to get laid. Meanwhile, Melisandre resurrects Jon, Bran tells Jon his real name is Gandalf Targaryen, and the entire North loses their shit.
Stannis shuts the hell up about his awesome claim to the Iron Throne, because Gandalf Targaryen's claim is so much better and he's come back from the dead, so they team up, re-take Winterfell, conscript freakin' everybody into the Night's Watch, and finally manage to man those dang towers along the Wall.
Daenerys continues her rampage North, accidentally burns King's Landing to the ground (oops, Cersei, shouldn't have left all that wildfire lying about!). Meanwhile, Cersei narrowly escapes and starts heading back to Casterly Rock when oops, Tyrion shows up on a dragon and accidentally lands on her. Squish. Killed by the valonqar.
Jamie and Brienne are forced to fight to the death. Brienne obviously wins because Jaime sucks left handed. Karma's a bitch Jamie, and Bran remembers thanks to the tree. Lady Stoneheart takes her group of merry men on North to besiege the Twins, but Daenerys just flies the fuck over those towers. There's NO WAY she's going to consent to marry one of Walder Frey's sons just to cross. Drogon drops a giant flaming turd on Walder's Solar, and the rest of the Freys let Daenery's ground forces through unmolested.
Everyone who's anyone now marches North to help Gandalf Targaryen battle the Others. The battle's hard, a lot of important POV characters and dragons die because quite frankly, we don't need half a hundred POVs of the same thing. It all ends in a duel between the Night King and Gandalf Targaryen, who gets helped by Brienne, Bran and his mom, Daenerys, and Barristan the Bold, and they kill him.
Daenerys marries Gandalf Targaryen...oh yeah, Quentyn dies of something - probably spear to the face or bloody flux, and they jointly rule Westeros from the Twins, getting mightily rich off the toll booth Walder had erected there. They have lots of babies and live happily ever after. The End.